Checking out www.singlescruise.com
. I haven't been but it seems to be the most popular single cruise co-ordinator. But like the other poster said this is probably a little bit older (or mixed) crowd.
Again I agree with the other poster:
Go on the Western route that the Triumph or Victory are doing (I've done this route three times). This is by far the most fun route. It has a late night stop on Cozumel that is a blast (skip dinner, get to Carlos and Charlies around 7:30, pace yourself).
The best time to go is mid-March - spring break time.
I'd vote on the Truimph over the Victory because you have a day to rest when you get home - but it really doesn't matter which one you go on. In fact looking at the dates I'd say the Victory mar 14 would be a good pick because it includes St Patrick's day.
Triumph: mar 6, mar 20
Victory: mar 14, mar 28
The last time I did this route there were a lot of nice young women on the ship. They were too young for me, but not for you. It won't be as crowded as Cancun - and that will probably be to your advantage.
Go. Have much fun. Go!